1/5th scale? The Saito FG 14B. I had a YS63 on my 1/5th cub and it was wonderful. Nice sound throttled back flying scale, but plenty of power to goof off, even with floats. In a gas 4-stroke this small...Saito is all that comes to mind. Save your pennies though....these little gasser 4-strokes aint free. The YS.63 and Saito .80 4 stroke glow engines are close in power, thus my suggestion for the FG14B. The Gasoline version of the Saito won't be quite as powerful, but still plenty in my opinion.